The countries that have the most used CNC machine stocks will vary depending on the market conditions and the industries that are prevalent in those countries. However, some countries that are known for having a large manufacturing sector, and therefore a high demand for CNC machines, include:

1. Germany: Germany is one of the leading manufacturing countries in Europe and is known for its high-precision engineering and machine-building industry. As a result, it is likely to have a large stock of used CNC machines.
2. United States: The United States has a large manufacturing sector and a strong economy, which has led to a high demand for CNC machines. This has resulted in a large stock of used CNC machines being available in the country.
3. Japan: Japan is another country with a strong manufacturing sector and is known for its high-precision engineering. As a result, it is likely to have a large stock of used CNC machines.
4. China: China has been rapidly developing its manufacturing sector in recent years, as a result, there is a large stock of used CNC machines available.
5. Italy, Taiwan, South Korea and Switzerland also have a strong manufacturing sector and a large stock of used CNC machines.

It’s important to note that the stock of used CNC machines also depends on the specific type of machine and the industries that are prevalent in that country.